5 things to consider before purchasing a microscope (for invertebrate ID)

GT Vision logoGT Vision is a UK optical microscope specialist and arehappy to assist with any technical questions you may have.

We supply and service the microscopes for the FSC BioLinks project and were asked if we could write a blog to advise those project volunteers that may now be considering purchasing a microscope of their very own for invertebrate identification.
Parts of a microscope
To help you understand which parts of the microscope we are referring to, please see the diagram above of the Ultra Zoom-2 stereo microscopes (the model that we supply to the FSC BioLinks project). Below are our top 5 considerations…

1.MAGNIFICATION

The magnification that you require will determine the type of microscope that you need. #

For most of the identification that is taught during the FSC BioLinks project you will require a lower magnification stereo microscope (also known as a dissecting microscope) which typically has magnifications of around 8x-50x. 

This includes looking at whole invertebrates such as spiders, bees or earthworms under the microscope, or parts thereof, that are not sliced into thin sections (e.g. for dissecting or identifying).

The normal magnification range of a stereomicroscope is perfect for the majority of applications but this can be changed with different eyepieces or auxiliary lenses on the front.

  • Higher power eyepieces increase magnification (for example, a pair of 20x eyepieces will double the standard magnification) but without an increase in resolution (or clarity in the fine detail).
  • Auxiliary objectives increase magnification and resolution but decrease the working distance.  For example, a 2x objective lens will double the magnification but greatly reduce the working distance.  A 0.5x objective lens halves the magnification but increases the working distance.

Again seek professional advise for what is best for your application.

For invertebrate identification techniques  viewing sections  (or even whole organisms in the case of smaller springtails) on slides at high magnification, you will need a compound microscope with higher magnifications of typically 40x-1000x.  

Stereo/dissecting microscopes are most commonly required for the groups covered by FSC BioLinks so the rest of this post will focus on stereo/dissecting microscopes.

2.WORKING DISTANCE

This is the space between the bottom of the microscope objective lens and the part of your specimen that is in focus.  It is the space available to position your hands and any tools under the microscope.  For purely identification purposes, you can usually get away with a smaller working distance.  If you are needing to do any dissecting or need to get any tools/tweezers under the microscope, you’ll need a stereo microscope with a longer working distance (we recommend over 100mm).

At this point it’s worth mentioning that typically the higher the magnification, the smaller the working distance. However, you can get some microscopes designed to have longer working distances. And, you can also add an auxiliary lens/objective to an existing microscope to decrease its magnification and increase its working distance, so check what optional extras are available for your model. This only applies to stereo zoom microscopes and single magnification stereo microscopes (not dual magnification stereo microscopes with a twisting turret/nosepiece).

3.LIGHTING

Lighting is absolutely crucial and of equal importance to the microscope itself!

  1. Halogen vs LED: Some cheaper and older models of microscopes have halogen illumination. The main point of note here is that halogen gives off a fair amount of heat; not ideal for many applications.  LED is a cold light (and more energy efficient).  Halogen also has a yellow glow, LED tends to produce a daylight whiter colour (sometimes with a hint of blue). So, LED’s provide a truer representation of the colour of the sample.
  2. Top (reflected) light vs bottom (transmitted) light:  If using a stereo microscope, you will most likely require reflected light.  Reflected light is used for viewing solid samples whereas transmitted illumination is used for viewing semi-transparent objects (biological sections on slides will use transmitted light compound microscopes).
  3. Different types of reflected lighting:  Most microscopes have their own basic top light built-in but this is almost always not enough.
    1. For bright, even illumination, an externally fitting ring light is a worthwhile investment.

    2. If you’re wanting to view difficult regions obscured by other parts of the specimen then you’ll need a set of twin goosenecks to give you that added flexibility to angle the light accordingly.

    3. If you’re viewing a ‘shiny’/highly reflective sample (eyes for example) you’ll need something to reduce the glare.  The best method for this is a diffused ring light to diffuse the light, but this can be rather costly so only really used for professional photography purposes and it also vastly reduces the working distance.  Another method is to use a polarising ring light.  This helps to reduce the glare with a cheaper price tag.  

4.CAMERA/PHOTOGRAPHY

Although it is possible to use DSLR cameras on microscopes and some people do get brilliant images, it’s not recommended due to the number of adapters and trial and error involved to get good image quality.  It’s a ‘faff’ and works out quite expensive. It is far simpler (and often cheaper!) to use a dedicated C-Mount fitting microscope camera.  Ideally, you’ll have a trinocular microscope that has a dedicated third port for the camera to attach to, but there are also eyepiece cameras options for those that only have binocular microscopes.  

          

5.BUDGET!

Stereo microscopes typically range in price from £200 - £5000 so you’ll need a rough idea of your budget.  

For £200 you get an entry level microscope.  Around £500-£1500 will get you a good quality microscope (that’s not one of the big four brands), such as our popular series of UltraZOOM Stereo Microscopes:

  • GXM UltraZOOM-1 – our entry-level stereo zoom microscope, from £409.32 + VAT for a complete system.
  • GXM UltraZOOM-2 – is the model of choice for the FSC BioLinks Project and with its long working distance (115mm), it’s perfect for any work involving tweezers/tools - from £837.90 + VAT for a complete system.
  • GXM UltraZOOM-3 – this has more advanced optics, a wider zoom range and a higher primary magnification of 7x-63x, reducing the need for extra eyepieces or auxiliary objectives. – from £966.60 + VAT for a complete system.

We’re always happy to recommend specific models based on your requirements with an unbiased opinion! Feel free to call us on 01284 789697 or email usommend specific models based on your requirements with an unbiased opinion! Feel free to call us on 01284 789697 or email us sales@gtvision.co.uk if you have any questions or would like more guidance.

Receive 12% off the UltraZOOM microscopes and any GX Microscopes products by entering the following code when checking out on the www.gtvision.co.uk website: FSC12 

Please note that this offer excludes the UltraZOOM-1, GX Value products and any non-GX Microscopes branded products.  The offer is valid until the 31st December, 2020.